Hitachi RAC-70YH7 Service Manual page 52

2. Buzzer Circuit
When the buzzer is to be activated, buzzer output pin
OFF repeatedly at 4kHz and Q301 is turned ON/OFF accordingly. A 4kHz voltage/frequency is applied to
the buzzer and the diaphragm of the buzzer vibrates to output 4kHz sound.
3. Initial setting (IC401)
The pre-heating operation start value, ratings of the compressor, maximum rotation speed, etc. are preset in
the micro computer.
4. Receive circuit
Infrared signals from the wireless remote controller are received by the light receiving unit and output after
being amplified and shaped.
12V
BZ1
B.Z
0V
5V
8 7 6 5
IC401
2
(E PROM)
1 2 3 4
0V
12V
R141
Receiver
Unit
0V
Micro computer
(AX-7X30)
30
BUZZER
of the micro computer alternates between ON and
30
5V
4 5 6
3 2 1
0V
Micro computer
SDA
26
(AX-7X30)
27
SCL
Micro computer
(AX-7X30)
R1109
13 REMOCON I/P
C1104
0V
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D401